I'm 10, thank you
Fine, lets pretend that this guys a retard
Heres the definition
for retard, its the second one if you can't figure it out
First off, the power source is called a psu (power supply unit) when it is used for computers.
Your keyboard, monitor, mouse, etc. is connected to something called a computer tower (case).
It has 6 sides: 5 you can see because one is the bottom.
If you would, refer to your manual and learn how to open your case
When you do so, there will be a small metal power box near the top towards the back.
Theres a label on the box.
Ok take a break, and try to reconcentrate. This might be getting too complicated.
Since you are "INCOMPETENT" with computers, how will you be able to install a graphics card?
Back to the topic: On the label, there should be a small chart with voltages and its amperage rating: the amount of power it can supply at one time.
Depending on the situation, most graphics cards would use a 12v supply line.
As "rx7i2" said, we would like to know what the amperage rating is
the Fortron power supply the people are referring to is this
For the more visual or illiterate learners, here a picture of a psu and its sticker: